OCT using spectrally resolved bandwidth

ABSTRACT

The embodiments disclosed herein is related to a system for optical coherence tomographic imaging of turbid (i.e., scattering) materials utilizing multiple channels of information. The multiple channels of information may be comprised and encompass spatial, angle, spectral and polarization domains. More specifically, the embodiments disclosed herein is related to methods and apparatus for utilizing optical sources, systems or receivers capable of providing (source), processing (system) or recording (receiver) a multiplicity of channels of spectral information for optical coherence tomographic imaging of turbid materials. In these methods and apparatus the multiplicity of channels of spectral information that can be provided by the source, processed by the system, or recorded by the receiver are used to convey simultaneously spatial, spectral or polarimetric information relating to the turbid material being imaged tomographically. The multichannel optical coherence tomographic methods can be incorporated into an endoscopic probe for imaging a patient. The endoscope comprises an optical fiber array and can comprise a plurality of optical fibers adapted to be disposed in the patient. The optical fiber array transmits the light from the light source into the patient, and transmits the light reflected by the patient out of the patient. The plurality of optical fibers in the array is in optical communication with the light source. The multichannel optical coherence tomography system comprises a detector for receiving the light from the array and analyzing the light. The methods and apparatus may be applied for imaging a vessel, biliary, GU and/or GI tract of a patient.

CROSS REFERENCE TO RELATE APPLICATIONS

The present application is a divisional application of U.S. patentapplication Ser. No. 11/446,683, filed Jun. 5, 2006, now U.S. Pat. No.7,783,337, which claims priority to U.S. Provisional Patent ApplicationSer. No. 60/687,930, filed Jun. 6, 2005, all incorporated by referencein their entirety herein.

TECHNICAL FIELD OF THE DISCLOSURE

The present disclosure relates to non-invasive systems methods ofmeasuring neural activity. More specifically, it relates todetermination of neural activity through measurement of transient;surface displacement of a neuron.

FIELD OF THE INVENTION

The embodiments disclosed herein is related to a system for opticalcoherence tomographic imaging of turbid (i.e., scattering) materialsutilizing multiple channels of information.

BACKGROUND

Myocardial infarction or heart attack remains the leading cause of deathin our society. Unfortunately, most of us can identify a family memberor close friend that has suffered from a myocardial infarction. Untilrecently many investigators believed that coronary arteries criticallyblocked with atherosclerotic plaque that subsequently progressed tototal occlusion was the primary mechanism for myocardial infarction.Recent evidence from many investigational studies, however, clearlyindicates that most infarctions are due to sudden rupture ofnon-critically stenosed coronary arteries due to sudden plaque rupture.For example, Little and coworkers (Little, W C, Downes, T R, Applegate,R J. The underlying coronary lesion in myocardial infarction:implications for coronary angiography. Clin Cardiol 1991; 14: 868-874,incorporated by reference herein) observed that approximately 70% ofpatients suffering from an acute plaque rupture were initiated onplaques that were less than 50% occluded as revealed by previouscoronary angiography. This and similar observations have been confirmedby other investigators (Nissen, S. Coronary angiography andintravascular ultrasound. Am J Cardiol 2001; 87 (suppl): 15A -20A,incorporated by reference herein).

The development of technologies to identify these unstable plaques holdsthe potential to decrease substantially the incidence of acute coronarysyndromes that often lead to premature death. Unfortunately, no methodsare currently available to the cardiologist that may be applied tospecify which coronary plaques are vulnerable and thus prone to rupture.Although treadmill testing has been used for decades to identifypatients at greater cardiovascular risk, this approach does not have thespecificity to differentiate between stable and vulnerable plaques thatare prone to rupture and frequently result in myocardial infarction.Inasmuch as a great deal of information exists regarding the pathologyof unstable plaques (determined at autopsy) technologies based uponidentifying the well described pathologic appearance of the vulnerableplaque offers a promising long term strategy to solve this problem.

The unstable plaque was first identified and characterized bypathologists in the early 1980's. Davis and coworkers noted that withthe reconstruction of serial histological sections in patients withacute myocardial infarctions associated with death, a rupture orfissuring of atheromatous plaque was evident (Davis M J, Thomas A C.Plaque fissuring: the cause of acute myocardial infarction, suddendeath, and crescendo angina. Br Heart J 1985; 53: 363-373, incorporatedby reference herein). Ulcerated plaques were further characterized ashaving a thin fibrous cap, increased macrophages with decreased smoothmuscle cells and an increased lipid core when compared to non-ulceratedatherosclerotic plaques in human aortas (Davis M J, Richardson P D,Woolf N, Katz D R, Mann J. Risk of thrombosis in human atheroscleroticplaques: role of extracellular lipid, macrophage, and smooth muscle cellcontent, incorporated by reference herein). Furthermore, no correlationin size of lipid pool and percent stenosis was observed when imaging bycoronary angiography. In fact, most cardiologists agree that unstableplaques progress to more stenotic yet stable plaques through progressionvia rupture with the formation of a mural thrombus and plaqueremodeling, but without complete luminal occlusion (Topol E J, RabbaicR. Strategies to achieve coronary arterial plaque stabilization.Cardiovasc Res 1999; 41: 402-417, incorporated by reference herein).Neo-vascularization with intra-plaque hemorrhage may also play a role inthis progression from small lesions (<50% occluded) to largersignificant plaques. Yet, if the unique features of unstable plaquecould be recognized by the cardiologist and then stabilized, a dramaticdecrease may be realized in both acute myocardial infarction andunstable angina syndromes, and in the sudden progression of coronaryartery disease.

The embodiments disclosed herein uses depth-resolved light reflection orOptical Coherence Tomography (OCT) to identify the pathological featuresthat have been identified in the vulnerable plaque. In OCT, light from abroad band light source or tunable laser source is input into aninterferometer with a portion of light directed to the vessel wall andthe other portion directed to a reference surface. The distal end of theoptical fiber is interfaced with a catheter for interrogation of thecoronary artery during a heart catheterization procedure. The reflectedlight from the plaque is recombined with the signal from the referencesurface forming interference fringes (measured by a photovoltaicdetector) allowing precise depth-resolved imaging of the plaque on amicron scale.

OCT uses narrow linewidth tunable laser source or a superluminescentdiode source emitting light over a broad bandwidth (distribution of wavelength) to make in situ tomographic images with axial resolution of10-20 μm and tissue penetration of 2-3 mm. OCT has the potential toimage tissues at the level of a single cell. In fact, the inventors haverecently utilized broader band width optical sources such asfemto-second pulsed lasers, so that axial resolution is improved to 4microns or less. With such resolution, OCT can be applied to visualizeintimal caps, their thickness, and details of structure includingfissures, the size and extent of the underlying lipid pool and thepresence of inflammatory cells. Moreover, near infrared light sourcesused in OCT instrumentation can penetrate into heavily calcified tissueregions characteristic of advanced coronary artery disease. Withcellular resolution, application of OCT may be used to identify otherdetails of the vulnerable plaque such as infiltration of monocytes andmacrophages. In short, application of OCT can provide detailed images ofa pathologic specimen without cutting or disturbing the tissue.

One concern regarding application of this technology to imageatherosclerotic plaques within the arterial lumen is the strongscattering of light due to the presence of red blood cells. Once acatheter system is positioned in a coronary artery, the blood flowbetween the OCT optical fiber and artery can obscure light penetrationinto the vessel wall. One proposed solution is the use of salineflushes. Saline use is limited in duration, however, since myocardialischemia eventually occurs in the distal myocardium. The inventors haveproposed the use of artificial hemoglobin in the place of saline.Artificial hemoglobin is non-particulate and therefore does not scatterlight. Moreover, artificial hemoglobin is about to be approved by theUnited States Food and Drug Administration as a blood substitute and cancarry oxygen necessary to prevent myocardial ischemia. Recently, theinventors demonstrated the viability of using artificial hemoglobin toreduce light scattering by blood in mouse myocardium coronary arteries(Villard J W, Feldman M D, Kim Jeehyun, Milner T E, Freeman G L. Use ofa blood substitute to determine instantaneous murine right ventricularthickening with optical coherence tomography. Circulation 2002; Volume105: Pages 1843-1849, incorporated by reference herein).

The first prototype of an OCT catheter to image coronary plaques hasbeen built and is currently being tested by investigators in Boston atHarvard-MIT (Jang I K, Bouma B E, Kang D H, et al. Visualization ofcoronary atherosclerotic plaques in patients using optical coherencetomography: comparison with intravascular ultrasound. JACC 2002; 39:604-609, incorporated by reference herein) in association with Light LabCo. The prototype catheter consists of a single light source and is ableto image over a 360 degree arc of a coronary arterial lumen by rotatinga shaft that spins the optical fiber. Because the rotating shaft ishoused outside of the body, the spinning rod in the catheter must rotatewith uniform angular velocity so that the light can be focused for equalintervals of time on each angular segment of the coronary artery.Mechanical drag in the rotating shaft can produce significant distortionand artifacts in recorded OCT images of the coronary artery.Unfortunately, because the catheter will always be forced to makeseveral bends between the entry point in the femoral artery to thecoronary artery (e.g., the 180 degree turn around the aortic arch),uneven mechanical drag will result in OCT image artifacts. As theapplication of OCT is shifted from imaging gross anatomical structuresof the coronary artery to its capability to image at the level of asingle cell, non-uniform rotation of the single fiber OCT prototype willbecome an increasingly problematic source of distortion and imageartifact.

Essentially, a current endoscope type single channel OCT systemdeveloped by Light Lab Co. suffers by non-constant rotating speed thatforms irregular images of a vessel target. See U.S. Pat. No. 6,134,003,incorporated by reference herein. Their approach of a rotary shaft tospin a single mode fiber is prone to produce artifact. The catheter willalways be forced to make several bends from its entry in the femoralartery, to the 180 degree turn around the aortic arch, to its finaldestination in the coronary artery. All these bends will cause unevenfriction on the rotary shaft, and uneven time distribution of the lighton the entire 360 degree arch of the coronary artery. As the applicationof OCT is shifted from gross anatomical structures of the coronaryartery to its capability to image at the level of a single cell, thennon-uniform rotation of the single fiber OCT will become even a greatersource of greater artifact.

The embodiments disclosed herein solve rotational distortion and relatedartifactual problems by developing a multiphase array OCT catheter. Byincorporating 10-60 individual OCT fibers within a single catheter,rotation of the optical fiber or similar element (e.g., micro-motordriven minor) and associated image distortion and artifacts areeliminated and spatial resolution may be improved. The catheter willallow 10-60 individual sources of light to independently image the 360degree arc of the coronary arterial lumen. An additional advantage ofthe multiphase array is provision of greater spatial resolution of theobject being interrogated in comparison to single fiber designs. Manyinvestigators recognize that a single rotating fiber or micro-motordriven minors utilized in current designs will not allow imaging at thelevel of a single cell while the multiphase array approach can providecellular resolution.

The construction of a multiphase array OCT catheter requires resolutionof a number of problems using innovative design solutions. Successfuldesign and demonstration of the catheter requires the development of anoptical channel containing 10-60 individual fibers in a 1.5 mm diameter.Each fiber requires a lens to focus the light, and a mirror fabricatedusing nanotechnology to redirect light from each fiber by 90 degreesfrom the catheter to the luminal surface of the coronary artery.Further, each of the 10-60 light paths has to be split again for bothreference and artery paths. The embodiments disclosed herein providedesign solutions to both the catheter and multichannel interferometer.

SUMMARY

The embodiments disclosed herein is related to a system for opticalcoherence tomographic imaging of turbid (i.e., scattering) materialsutilizing multiple channels of information. The multiple channels ofinformation may be comprised and encompass spatial, angle, spectral andpolarization domains. More specifically, the embodiments disclosedherein is related to methods and apparatus utilizing optical sources,systems or receivers capable of providing (source), processing (system)or recording (receiver) a multiplicity of channels of spectralinformation for optical coherence tomographic imaging of turbidmaterials. In these methods and apparatus the multiplicity of channelsof spectral information that can be provided by the source, processed bythe system, or recorded by the receiver are used to conveysimultaneously spatial, spectral or polarimetric information relating tothe turbid material being imaged tomographically.

The multichannel optical coherence tomographic methods can beincorporated into an endoscopic probe for imaging a patient. Theendoscope comprises an optical fiber array and can comprise a pluralityof optical fibers adapted to be disposed in the patient. The opticalfiber array transmits the light from the light source into the patient,and transmits the light reflected by the patient out of the patient. Theplurality of optical fibers in the array is in optical communicationwith the light source. The multichannel optical coherence tomographysystem comprises a detector for receiving the light from the array andanalyzing the light. The methods and apparatus may be applied forimaging a vessel, biliary, GU and/or GI tract of a patient.

The embodiments disclosed herein pertain to an endoscope for a patient.The endoscope comprises a light producing means, such as a light source.The endoscope comprises an optical fiber array comprising a plurality ofoptical fibers adapted to be disposed in the patient. The optical fiberarray transmits the light from the light producing means into thepatient, and transmits the light reflected by the patient out of thepatient. The plurality of the optical fibers of the array in opticalcommunication with the light producing means. The endoscope comprises adetector for receiving the light from the array and analyzing the light.The plurality of the optical fibers of the array in opticalcommunication with the detector.

The embodiments disclosed herein pertain to a method for imaging apatient. The method comprises the steps of transmitting light from alight source into an optical fiber array comprising a plurality ofoptical fibers in the patient. There is the step of transmitting thelight reflected by the patient out of the patient. There is the step ofreceiving the light from the array at a detector. There is the step ofanalyzing the light with the detector.

The embodiments disclosed herein pertain to an apparatus for studying anobject. The apparatus comprises means for producing light. The apparatuscomprises means for analyzing the light that has reflected from theobject based on polarization, space, position or angle.

The embodiments disclosed herein pertain to an apparatus for studying anobject. The apparatus comprises means for producing light. The apparatuscomprises means for analyzing the light that has reflected from theobject based on polarization.

The embodiments disclosed herein pertain to an apparatus for studying anobject. The apparatus comprises means for producing light. The apparatuscomprises means for analyzing the light that has reflected from theobject based on space.

The embodiments disclosed herein pertain to an apparatus for studying anobject. The apparatus comprises means for producing light. The apparatuscomprises means for analyzing the light that has reflected from theobject based on angle.

The embodiments disclosed herein pertain to a method for studying anobject. The method comprises the steps of producing light. The methodcomprises the steps of analyzing the light that has reflected from theobject based on polarization, space, position or angle.

The embodiments disclosed herein pertain to a method for studying anobject. The method comprises the steps of producing light. The methodcomprises the steps of analyzing the light that has reflected from theobject based on polarization.

The embodiments disclosed herein pertain to a method for studying anobject. The method comprises the steps of producing light. The methodcomprises the steps of analyzing the light that has reflected from theobject based on space.

The embodiments disclosed herein pertain to a method for studying anobject. The method comprises the steps of producing light. The methodcomprises the steps of analyzing the light that has reflected from theobject based on angle.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, the preferred embodiment are disclosed andthe preferred methods of practicing the embodiments disclosed herein areillustrated in which:

FIG. 1 is a schematic representation of an overview of the embodimentsdisclosed herein.

FIG. 2 is a top view of an input arm (light source) of the embodimentsdisclosed herein.

FIG. 3 is a schematic representation of a side view of the input arm(light source).

FIG. 4 is a schematic representation of a fiber based solution for theinput arm.

FIG. 5 is a schematic representation of a side view of the sample arm.

FIG. 6 is a schematic representation of an axial view of the sample arm.

FIG. 7 is a schematic representation of a top view of an axicon lens.

FIG. 8 is a schematic representation of an optical fiber array of thesample arm.

FIG. 9 a is a schematic representation of a perspective view of a probetip of the sample arm emphasizing the mirrors to refocus the light onthe tissue of interest; and FIG. 9 b is a cross-sectional view the probetip and the sample arm to refocus the light away from the probe tip.

FIG. 10 is a schematic representation of a side view of a groove of thetip with an attached fiber ending with a 45° angled mirror (reflection).

FIG. 11 is a schematic representation of a top view of the tip with anattached fiber.

FIG. 12 is a schematic representation of a first step of manufacture ofeach fiber lens of the sample arm.

FIG. 13 is a schematic representation of a second step in themanufacture of each fiber lens of the sample arm.

FIG. 14 is a schematic representation of a reference arm of theembodiments disclosed herein.

FIG. 15 is a schematic representation of a top view of a detection armof the embodiments disclosed herein.

FIG. 16 is a schematic representation of a side view of the detectionarm.

FIGS. 17 a and 17 b are alternative schematic representations of ascanning probe of the sample arm.

FIGS. 18 a and 18 b are schematic representations of a hydraulicmechanism.

FIGS. 19 a and 19 b are schematic representations of exploded views ofthe hydraulic mechanism.

FIGS. 20 a-20 d are schematic representations of different views of atwisted shaft of the hydraulic mechanism.

FIGS. 21 a and 21 b are schematic representations of the fiber-shaftholder.

FIGS. 22 a-22 c are schematic representations of fiber grooves.

FIG. 23 is a side view of the micro-mirror.

FIG. 24 is a perspective view of the micro-mirror.

FIG. 25 is a perspective view of the micro-mirror with a portionirradiated by the laser beam.

FIG. 26 is a perspective view of the micro-minor having a deformationgenerated from being irradiated by a laser beam as shown in FIG. 25.

FIG. 27 is a schematic representation of the micro-mirror beingcontinuously heated by a laser beam shining on different locations ofthe micro-minor.

FIG. 28 is a schematic representation of the resulting changing of thetilting direction of the micro-mirror because of the changing locationof the laser beam on the micro-mirror.

FIG. 29 is a schematic representation of the micro-mirror in the probecover relative to the fibers.

FIG. 30 is a schematic representation of the micro-mirror movementrelative to the fiber.

FIG. 31 is a schematic diagram of single channel fiber-basedpolarization sensitive spectral domain optical coherence tomography witha fiber optic spectral polarimetry instrument (FOSPI).

FIG. 32 is a schematic representation of a fiber-based spatiallymultiplexed swept source optical coherence tomography.

FIG. 33 is a schematic representation of a multi-fiber angle-domain OCT.

FIGS. 34 and 35 are images recorded with a spatially multiplexed OCTsystem.

FIGS. 36 and 37 are graphs of phase retardation due to birefringence andfast-axis angle, respectively.

DETAILED DESCRIPTION

Referring now to the drawings wherein like reference numerals refer tosimilar or identical parts throughout the several views, and morespecifically to FIGS. 1-5, 15 and 16 thereof, there is shown anendoscope 10 for a patient. The endoscope 10 comprises means 102 forproducing light, such as a light source 51. The endoscope 10 comprisesan optical fiber array 28 comprising a plurality of optical fibers 8adapted to be disposed in the patient. The optical fiber array 28transmits the light from the producing means, preferably including alight source 51, into the patient, and transmits the light reflected bythe patient out of the patient. The plurality of the optical fibers 8 ofthe array 28 is in optical communication with the light producing means102. The endoscope 10 comprises a detector D for receiving the lightfrom the array 28 and analyzing the light. The plurality of the opticalfibers 8 of the array 28 is in optical communication with the detectorD.

Preferably, the endoscope 10 includes a tube 53 about which theplurality of optical fibers 8 are disposed. The tube 53 preferably hasgrooves 54 that extend longitudinally along the tube 53, as shown inFIG. 10. One of the plurality of optical fibers 8 is disposed in each ofthe grooves 54. Preferably, the endoscope 10 includes a probe tip 55, asshown in FIG. 11, having a reflector 56 disposed in each groove whichreflects light from the optical fiber 8 in the groove when the reflector56 is in the patient and reflects light from the patient to the opticalfiber 8 when the array 28 is in the patient.

The light source 51 preferably includes a coherent light source 51 andmeans 57 for guiding the light from the light source 51 to the pluralityof optical fibers 8 of the array 28. Preferably, the optical fiber 8 issingle mode, has a core 118 with cladding 120 disposed about the core118, and has a lens 122 at its tip which focuses the light from the core118 to the reflector 56 and light from the reflector 56 to the core 118,as shown in FIGS. 12 and 13. The array 28 preferably includes atransparent cover 7.

Preferably, the light source 51 comprises an input arm 58, the array 28comprises a sample arm 59, the detector D comprises a reference arm 60and a detector arm 61; and the input arm 58, the detector arm 61, thesample arm 59 and the reference arm 60 together form an interferometer.The reference arm 60 preferably uses RSOD to introduce depth scanningand dispersion compensation to the interferometer.

Preferably, the endoscope 10 includes an opto-coupler 62 which opticallycouples corresponding optical fibers 8 of the input arm 58, sample arm59, reference arm 60 and detector arm 61 together. The detector Dpreferably determines structural information about the patient from theintensity of an interference signal from reflected light fromcorresponding fibers of the sample arm 59 and the reference arm 60having a same bypass length.

Preferably, the probe tip 55 includes a scanning head 1 which holds Noptical fibers 8, where N is greater than or equal to 2 and is aninteger, as shown in FIGS. 17-22 c. The N optical fibers 8 arepreferably arranged around the scanning head 1 in parallel and equalspacing. Preferably, the probe tip 55 includes a mechanism 134 formoving the scanning head 1 so each of the optical fibers 8 scan anangular range of N/360 degrees. The moving mechanism 134 preferablyincludes a mechanism 9 for linear motion which causes the scanning head1 to rotate.

Preferably, the linear motion mechanism 9 includes a fiber shaft holder3 having a shaft channel 31 extending axially along the holder 3, and Nfiber channels 32 are arranged around the holder 3 in parallel with theshaft channel 31, and a twisting shaft 4 that fits in and conforms withthe shaft channel 31, as the shaft 4 moves in the channel 31, the holder3 rotates.

The scanning head 1 preferably has a socket head 12 that conforms withthe shaft 4 and causes the scanning head 1 to rotate. Preferably, theprobe tip 55 includes a guide wire holder 57 disposed on the scanningprobe 50 which receives and follows a guide wire 56 when the guide wire56 is in a blood vessel, biliary tract, and possible GU tract. A guidewire 56 is not necessary in the GI tract. Preferably, the endoscope 10includes a spring 6 disposed between the scanning head 1 and the fibershaft holder 3 which forces the shaft 4 back after the shaft 4 has movedforward.

The embodiments disclosed herein pertain to a method for imaging avessel, GU, GI or biliary tract of a patient. The method comprises thesteps of transmitting light from a light source 51 into an optical fiberarray 28 comprising a plurality of optical fibers 8 in the patient.There is the step of transmitting the light reflected by the patient outof the patient. There is the step of receiving the light from the array28 at a detector D. There is the step of analyzing the light with thedetector D.

Preferably, there are the steps of reflecting light from each opticalfiber 8 with a corresponding reflector 56 associated with the fiber, andreflecting light from the patient to the associated fiber with areflector 56. There is preferably the step of moving each of N opticalfibers 8 comprising the optical fiber array 28 an angular range of N/360degrees. Preferably, there is the step of applying a linear motion tocause each of the N optical fibers 8 of the optical fiber array 28 tomove the angular range.

The step of applying the linear motion preferably includes the step ofmoving axially forward in parallel with the N optical fibers 8 atwisting shaft 4 through a shaft channel 31 extending axially along afiber shaft holder 3 having N fiber channels 32 arranged around theholder 3 in parallel with the shaft channel 31 which causes the holder 3to rotate. Each of the N optical fibers 8 is disposed in a respectivefiber channel 32 of the N fiber channels 32. The twisting shaft 4 fitsin and conforms with the shaft channel 31, as the shaft 4 moves in thechannel 31. Preferably, there is the step of guiding the optical fiberarray 28 along a guide wire 56 which is received by a guide wire holder57 when the guide wire 56 is in a blood vessel, biliary tract, andpossibly GU system, but not in the GI tract.

The embodiments disclosed herein pertain to an apparatus for studying anobject. The apparatus comprises means for producing light. The apparatuscomprises means for analyzing the light that has reflected from theobject based on polarization, space, position or angle.

The means for analyzing is preferably described in the figures, wherepolarization is found in FIG. 31, position in FIGS. 1-30, space in FIG.32, and angle in FIG. 33.

The embodiments disclosed herein pertain to an apparatus for studying anobject. The apparatus comprises means for producing light. The apparatuscomprises means for analyzing the light that has reflected from theobject based on polarization.

The embodiments disclosed herein pertain to an apparatus for studying anobject. The apparatus comprises means for producing light. The apparatuscomprises means for analyzing the light that has reflected from theobject based on space.

The embodiments disclosed herein pertain to an apparatus for studying anobject. The apparatus comprises means for producing light. The apparatuscomprises means for analyzing the light that has reflected from theobject based on angle.

The embodiments disclosed herein pertain to a method for studying anobject. The method comprises the steps of producing light. The methodcomprises the steps of analyzing the light that has reflected from theobject based on polarization, space, position or angle.

The embodiments disclosed herein pertain to a method for studying anobject. The method comprises the steps of producing light. The methodcomprises the steps of analyzing the light that has reflected from theobject based on polarization.

The embodiments disclosed herein pertain to a method for studying anobject. The method comprises the steps of producing light. The methodcomprises the steps of analyzing the light that has reflected from theobject based on space.

The embodiments disclosed herein pertain to a method for studying anobject. The method comprises the steps of producing light. The methodcomprises the steps of analyzing the light that has reflected from theobject based on angle.

In the operation of the embodiments disclosed herein, a near infraredbroadband light source 51 sends a light beam into the input arm 58 ofthe array type interferometer. The beam profile from the light source 51is a circular gaussian. The optics before connector 1 makes the beamprofile linear and focuses it into the connector 1. The array typeinterferometer consists of a multiple fiber-based interferometer thathas four fiber arms connected to an opto-coupler 62. Incoming light intothe input arm 58 is divided to the sample and reference arms 59, 60,respectively. In the sample arm 59, optical fibers 8 are distributedlike an annular ring, and light will be focused at the target vesselperpendicular to the optical axis. In the reference arm 60, RSODintroduces depth scanning and dispersion compensation. When thereflected light from both arms have the same light path length, strictlyspeaking within a coherence length, interference occurs. The intensityof the interference signal represents the structural information of asample.

More specifically, in regard to the input arm 58, and referring to FIGS.1, 2 and 3, a single beam comes out of Si and will be collimated by L1.At this point, the beam diameter is big enough to project across all ofC1's area, but the beam is still circular. CL1 and CL2, circular lenses,change the beam profile to a linear shape, which means that the beam isnot circular anymore, but it looks narrow from FIG. 2 and the same shapewith the beam after L1 on FIG. 3. ML1 focuses all light onto C1.

This is known as an open optic solution:

Light source S1 has a fiber tip from which light departs into air.

L1 is a collimating lens 122, so the fiber tip of the light source 51should be located at the back of the focal point of L1 in order tocollimate the light.

CL1, CL2 are cylindrical lenses. Separation between the two is the sumof the focal Length of each cylindrical lens. They work as a telescopewhich decreases beam size only in one direction. In other words, thesize of the beam does not change from FIG. 3.

ML1 is a micro lens array, which has a lot of small lenses. Each of thesmall lenses is positioned to have a focal point at each fiber entranceof C1. C1 should be located at the focal point of ML1. All micro lenseshave same focal length. C1 is a linear fiber array 28.

In an alternative embodiment of the input arm 58, as shown in FIG. 4,known as a fiber based solution:

Light source S1 is connected to a single mode fiber, which is connectedto fiber splitter (50:50), S1.

The first fiber splitter is 1 by 2. Each output end of the 1*2 fibersplitter is connected to one 1*4 splitter, SP1.

Each output end of the 1*4 splitter, 2nd layer, is connected to another1*4 splitter, 3rd layer, SP2.

At the output of the 3rd layer, the number of fibers is 32. The 32fibers comprise a linear fiber array 28, SP3.

Linear Fiber Array 28:

Each fiber is a single mode fiber, which can have a different cutofffrequency. The cutoff frequency is dependent on the center wavelength ofthe light source 51. Usually, 850 nm or 1300 nm of center wavelength forthe light source 51 are used.

Each fiber is attached to another so that all together they form alinear fiber array 28.

C1 is connected to multiple interferometers. Each interferometerconsists of four fiber arms and opto-coupler 62. At each end of eacharm, there is a linear array 28 fiber connector (C1, C2, C3, and C4).Incoming light will be divided by the opto-coupler 62 into the sampleand reference arms 59, 60, respectively.

With respect to the sample arm 59, this sample arm 59, as shown in FIGS.5, 6, 7, 8 and 17, goes into the target vessel. C2 is connected to alinear fiber array 28 which is of an annular shape at the other end. Thetotal length of the arm will be around 2˜3 m. When the light leaves theannular tip F, it will be collimated by L1 and then reflected by L2outward from the probe.

Reflected light from tissue will follow back to L2 and L1 and begathered by the fiber Tip F. Later, two reflected lights from the sampleand reference arms 59, 60, respectively, will make interference, whichwill be detected by the detector D at the detector arm 61.

The sample arm 59 is supposed to go through a target vessel, GI, GU orbiliary tract. C2 is connected to a linear fiber array 28 which has anannular shape at the other end (probe tip 55) (FIG. 8). Total length ofthe sample arm 59 is about 1.5 m. The fiber array 28 will be molded by atransparent cover 7 material (ex: silicon resin or polymers).

At the annular probe tip 55 shown in FIGS. 9 a and 9 b, each fiber 8 isglued at a groove 54 of a cylindrical polymer tube 53. The shape of eachgroove 54 is shown at FIGS. 10 and 11. Each groove end has a reflector56 which is 45° oblique to axial direction. The groove 54 will be madeby micro fabrication technique. Each fiber 8 has a lens 122 at the tip,which can be manufactured by splicing a multimode fiber with the samediameter of the cladding 120 of the single mode fiber and then meltingthe end of multimode fiber in order to get curvature (FIGS. 12 and 13).When the light leaves the fiber tip, the light will be reflected outwardby the reflector 56 at the end of the groove 54, and then will befocused at the target tissue area. Reflected light from the tissue willfollow back the same path as the incoming light, and go to the detectorarm 61.

Micromachining or micro-electro-mechanical systems (MEMS) andnanotechnology are becoming increasingly popular for the development ofimproved biomaterials and devices (Macilwain C., “US plans large fundingboost to support nanotechnology boom,” Nature, 1999; 400:95,incorporated by reference herein). Similar to manufacturing methods usedfor computer microchips, MEMS processes combine etching and/or materialdeposition and photolithographic-patterning techniques to developultrasmall devices (Madou, M., “Fundamentals of microfabrication,” CRCPress: Boca Raton, 2002, incorporated by reference herein). MEMS hasbeen proven promising in medicine for its small mass and volume, lowcost, and high functionality. Successful MEMS devices in medicineinclude smart sensor for cataract removal, silicon neurowells,microneedles for gene and drug delivery, and DNA arrays (Polla, D. L.,Erdman, A. G., Robbins, W. P., Markus, D. T., Diaz-Diaz, J., Rizq, R.,Nam, Y., Brickner, H. T., Wang, A., Krulevitch, P., “Microdevices inMedicine,” Annu. Rev. Biomed. Eng., 2000; 02:551-76; McAllister et al.,2000, both of which are incorporated by reference herein). However, mostof the MEMS processes are planar in nature for two-dimension (2D)micro-features and primary for processing silicon material. Othermicromachining processes include laser beam micromachining (LBM),micro-electrical discharge machine (micro-EDM), and electron beammachining (EBM) (Madou, M., “Fundamentals of microfabrication,” CRCPress: Boca Raton, 2002), incorporated by reference herein.Micro-fabrication and micro-device development using metals, metalalloys, silicon, glass, and polymers are described in the following.(Chen, S. C., Cahill, D. G., and Grigoropoulos, C. P., “TransientMelting and Deformation in Pulsed Laser Surface Micro-modification ofNi—P Disks,” J. Heat Transfer, vol. 122 (no. 1), pp. 107-12, 2000;Kancharla, V. and Chen, S. C., “Fabrication of BiodegradableMicrodevices by Laser Micromachining of Biodegradable Polymers,”Biomedical Microdevices, 2002, Vol. 4(2): 105-109; Chen, S. C.,Kancharla, V., and Lu, Y., “Laser-based Microscale Patterning ofBiodegradable Polymers for Biomedical Applications,” in press,International J. Nano Technology, 2002; Zheng, W. and Chen, S. C.,“Continuous Flow, nano-liter Scale Polymerase Chain Reaction System,”Transactions of NAMRC/SME, Vol. 30, pp. 551-555, 2002; Chen, S. C.,“Design and Analysis of a Heat Conduction-based, Continuous Flow,Nano-liter Scale Polymerase Chain Reaction System,” BECON, 2002, all ofwhich are incorporated by reference herein).

For the array 28, a stainless steel cylinder is chosen with a diameterof 1.5 mm as the base material. The diameter is 1.0 mm for vascularapplications, larger for GU, GI and biliary applications, up to 3.0 mm,if desired. Both the micro-grooves 54 (or micro-channels of 200 micronswide) and the reflecting surfaces are machined by micro-electricaldischarge machining (micro-EDM) or micro-milling using focused ionmachined tool. To enhance the reflectivity of the reflecting surface,the stainless steel cylinder is coated with evaporated aluminum usingelectron-beam evaporation.

In regard to the reference arm 60, shown in FIG. 14, light is collimatedby L1 after leaving connector C4, spectrally distributed by a grating(G1) and focused to a minor (GA1). By vibrating GA1, the light pathlength will be changed in order to achieve depth scanning.

There are many options to build the reference arm 60 applying existingtechniques. A very simple form of the reference arm 60 has just a mirrorattached onto a voice coil that is driven by a function generator withsine wave. The light reflects back by the mirror and the minor positionchanges the light path length. This path length change provides depthscanning of the target tissue because interference occurs only when botharms have the same light path length. Preferably, the reference arm 60is more complicated than the simple one. That is called Rapid-ScanningOptical Delay (RSOD) which can provide fast depth scanning anddispersion compensation.

Linear array type beam launches from C4, and is collimated by L1. Aminor (M1) reflects the beam to a grating (G1) which spectrallydistributes the broadband source light. Spectrally distributed lightwill be focused on a Galvono-scanning minor (GA1) by a lens (L2).Separation between G1 and L2 determines the amount of chromaticdispersion degree so any material dispersion can be compensated forusually caused by fibers. The beam offset from the scanning mirrorcenter determines the fringe frequency that will show up afterinterfering two reflected lights. The reflected light from the GA1 goesto L2, G1, and to mirror M2. And then the light reflected following backincoming path and will be coupled back to C4.

Referring to the detector arm 61, as shown in FIGS. 15 and 16, light iscollimated by L1 after leaving connector C3, and is circular.Combination of CL1 and CL2 makes the beam look linear in one plane(horizontal). Micro-lens array ML1 makes the light focus on the arraydetector D.

As shown in FIGS. 17 a, 17 b, 19 a, and 19 b, the scanning probe 50 iscomprised of a scanning head 1, a fiber-shaft holder 3, a twisted shaft4, a transparent cover 7, a guide wire holder 2, and a mechanism 9 forlinear motion. In this embodiment, the scanning head 1 is adapted tohold a fiber bunch that contain 20 optical fibers 8, which are arrangedaround the scanning head 1 in parallel and equal spacing. In operation,each of the fibers is set to scan an angular range of 18 degrees(360°/20=18°.). Reflective surfaces 11 are formed on the scanning head 1and are oriented 45° degrees to the central axis of each respectiveoptical fibers 8, such that they would guide the light from the fiberbunch and direct the light through the transparent cover 7.

The scanning head 1 is designed to provide an 18 degrees' back-and-forthrotation. The back-and-forth rotation realizes the scanning functionrequired by the OCT system. The mechanism of this back-and forthrotation is described below.

The fiber-shaft holder 3 is substantially a multi-tubular structure. Itis formed with one shaft channel 31 extending along the central axis ofthe fiber-shaft holder 3 and 20 fiber channels 32 arranged around thefiber-shaft holder 3 in parallel. The optical fibers 8 extend throughrespective fiber channels 32. The shaft channel 31 has a roundcross-sectional area. At the upper end of the shaft channel 31, theshaft channel 31 is an opening, but the geometry of the opening isreduced from the round cross-sectional area to a rectangularcross-sectional hole 311. The reason for this structural design will bedescribed along with the description of the twisted shaft 4.

The twisted shaft 4 has a rectangular cross-section area, which isidentical in geometry to the rectangular cross-sectional hole 311 of thefiber-shaft holder 3. Indicated by its name, the shaft 4 is partiallytwisted along the shaft central axis and can be divided into anon-twisted part 41 and a twisted part 42. In assembly, the shaft 4 ispassed through the rectangular cross-sectional hole 311 of thefiber-shaft holder 3, and it is enabled to slide back-and-forth via therectangular cross-sectional hole 311. The relative motion of thesurfaces of the rectangular cross-sectional hole 311 and the twistedshaft 4 form the mechanism that realizes a back-and-forth rotation. Thereason is that when the twisted part 42 of the shaft 4 slides throughthe rectangular cross-sectional hole 311, the shaft 4 itself is forcedto rotate along the shaft central axis to fit the matching of both thesurfaces of the rectangular cross-sectional hole 311 and the twistedshaft 4. Particularly, the shaft 4 and the holder 3 compose a mechanism9 that can transmit a linear motion into a rotational motion.

The description is now focused on the scanning head 1. The scanning head1 has a rectangular socket 12, which has a cross-section area identicalto that of the twisted shaft 4. The rectangular socket 12 provides achannel covering the non-twisted part 41 of the twisted shaft 4 and letsthe non-twisted part 41 exert the back-and forth motion inside therectangular socket 12. The moving range of the shaft 4 is constrainedsuch that the twisted part 42 does not pass into the scanning head'srectangular socket 12 (that will result in a geometric mismatch), butthe twisted part 42 only interacts with the fiber-shaft holder'srectangular cross-sectional hole 311. According to the descriptionabove, the motion of the shaft 4 is comprised of a linear component (V)and an angular component (ω). Referring to the geometry of therectangular socket 12 and non-twisted part 41 of the shaft 4, the shaftmotion's linear component (V) would not contribute to the motion of thescanning head 1 (regardless of the friction between the surfaces), butthe angular component (ω) does. The scanning head 1 rotates back andforth with the rotational motion of the twisted shaft 4, which in turnresults from the twisted shaft's linear back-and-forth movement relativeto the fiber-shaft holder 3. As a result, the scanning head 1 provides aback-and-forth rotational motion transmitted from the back and forthlinear motion provided by the twisted shaft 4.

A guide wire holder 57 is a module used to guide the scanning probe 50toward the investigated section of the detected blood vessel, biliaryduct, and possibly GU application. For the GI tract, a guide wire 56 isgenerally not used. In operation, a guide wire 56, or “guide tissue”, ispreviously disposed along a specific route of human vessels, such that atrack for the scanning probe 50 of the OCT system can be formed. Theguide wire holder 57 constrains the scanning probe 50 such that it canonly slide along the track formed by the guide wire 56. The scanningprobe 50 is therefore guided to the patient section to be investigated.

Guide wire holder 57 and a scanning head holder 5 function as bearingsof the scanning head 1. They constrain the movement of the scanning head1 and stabilize it. As well, a compressive spring 6 is disposed betweenthe scanning head 1 and the fiber-shaft holder 3. The spring 6 is mildlycompressed in assembly, such that it pushes the scanning head 1 againstthe scanning head holder 5 and eliminates any potential axial movementof the scanning head 1 that may result in axial positioning errors (Ad).It is preferable that the spring 6 supplies torque between the scanninghead 1 and the fiber-shaft holder 3. The spring 6 has both its ends,respectively, fixed on the scanning head 1 and the fiber-shaft holder 3.The spring 6 is mildly twisted in assembly. By this means, the spring 6can provide a torque to the back-and-forth rotational mechanism, suchthat the backlash (resulting from, for example, the tolerance betweenthe rectangular cross-sectional hole 311 and the shaft 4) of therotational mechanism, as well as the resultant angular positioningerrors (Δθ), are eliminated.

Note that, the cross-sectional geometry of the shaft channel 31 iscircular. With respect to the shaft channel 31, the twisted shaft 4 isformed with a cylinder part 43 at its end of the twisted part 42. Thecylinder part 43 and the shaft channel 31 perform a motion like apiston. In an upward movement of the twisted shaft 4, due to thegeometric difference, the cylinder part 43 would be blocked at the edge33 of the rectangular cross-sectional hole 311 of the fiber-shaft holder3 and provide an upper stopper 33 for the twisted shaft 4. On the otherhand, a lower stopper 34 is placed to block the cylinder part 43 in adownward movement. The function of the upper and lower stoppers 33, 34is helpful in controlling the movement of the twisted shaft 4, as wellas controlling the angular motion of the scanning head 1.

There are many methods in the prior art that are able to provide thepower for the mechanism to push and pull the twisted shaft 4 to generatethe linear movement. However, hydraulic force, particularly fluidicpressure, is preferred due to the following advantages:

1. Electricity is not required to be transmitted into the scanning head1 to energize a hydraulic linear mechanism 9. Some of the mechanisms,such as electromagnetic systems (or more particularly, somemicro-motors), require not only electricity to be energized, but alsoadditional components, e.g., coils or magnets, installed to the scanninghead 1 to transform the electrical energy into mechanical momentum. Theuse of electricity is not preferable for medical issues; and therequirement of additional components would increase the technicaldifficulty in manufacturing and the complexity of the whole system. Someof the other mechanisms, like those comprising piezoelectric materials,can be composed with little space and simple structure, but they stillneed to receive a large voltage to generate the required momentum.

2. A hydraulic mechanism 9 takes little space.

The structure of the hydraulic mechanism 9 is illustrated in FIGS. 18 aand 18 b. The hydraulic mechanism 9 can be simply a liquid conduit thatguides liquid, such as water, to push or pull the piston systemcomprised of the cylinder part 43 and the shaft channel 31. Consideringthat leakage through the gap of a piston system may result inundesirable problems, the hydraulic mechanism 9 is, preferably,comprised of a micro-balloon 91 made by a polymeric thin film. As shownin FIGS. 18 a and 18 b, the twisted shaft 4 is in its lower positionwhen the balloon 91 is flat (FIG. 18 a). As water is pumped into thepiston system, the balloon 91 becomes turgid, and the twisted shaft 4 ispushed toward its upper position with an 18 degree spin (FIG. 18 b). Therequired back-and forth motion can be generated by switching the flatand turgid states of the micro-balloon 91.

For a single fiber OCT system, a scan rate of 6 rev/sec (6 Hz) issatisfactory [Andrew M. Rollins et al., “Real-time in vivo imaging ofhuman gastrointestinal ultrastructure by use of endoscopic opticalcoherence tomography with a novel efficient interferometer design”,OPTICS LETTERS, Vol. 24, No. 19, Oct. 1, 1999, incorporated by referenceherein]. That means in one second the OCT system should be able toprovide at least 6 pictures illustrating the cross-sectional data of thevessel. The scanning probe 50 has 20 fibers, so the satisfactory scanrate can be reduced to 0.3 Hz (6/20=0.3), which is much slower and mucheasier to be realized by the hydraulic actuating system. Ideally, 15pictures/sec. is required for optimal image resolution.

Rather than continuous rotation, the scanning probe 50 operates in aback-and-forth manner, so that the angular speed of the scanning head 1will not be constant even when the whole system reaches its steadystate. During operation, therefore, detecting the angle of the scanninghead 1, as well as figuring out the angular position that the scanneddata belongs to, are important issues. The angle of the scanning head 1can be simply approximated by comparing the output effort of the pumpingsystem with a reference curve obtained from previous experiments. Moreprecise detection can be reached by the analysis of the feedback of theoptical signals. For example, analyzing the Light Doppler Effect [VolkerWestphal at al., “Real-time, high velocity-resolution color Doppleroptical coherence tomography”, OPTICS LETTERS, Vol. 27, No. 1, Jan. 1,2002, incorporated by reference herein] of the feedback signals isanother method.

The twisted shaft 4 can be formed by precise CNC machining that is wellknown in the industry. A thin round shaft, minimum diameter 1.0 mm, maybe used as the intrinsic material before the machining. For production,two ends of the round shaft are clamped, its central portion isprecisely milled and four orthogonal planes on the central portion aregenerated. The planes define the rectangular cross-section of thetwisted shaft 4 (forming a long shaft in this step), as shown in FIG. 20a. Following the milling, one of the two clamps holding the shaft isrotated relative to the other clamp to twist the shaft a specific angleabout its central axis. The twisted part 42 of the twisted shaft 4 isthus formed.

Following the twisting step, the rotated clamp is released to free theelastic distortion of the shaft 4 (with its plastic distortionremaining), and then the clamp is tightened again. At the next step, asshown by FIG. 20 b, the shaft 4 is milled again at one side of itsstill-round portion, thereby generating another rectangular portion 41that is untwisted.

The cylindrical portion 43 (which serves as a piston) is formed from theround portion of the shaft 4. A precise lathing could further be used tofix the central axis and diameter of the cylindrical part. As shown inFIG. 20 c, only a short portion of the shaft 4 is required. The excessportion of the shaft part is cut off.

As shown in FIG. 21 a, the fiber-shaft holder 3 can be combined with twoparts, A and B. The part A is actually the body of the catheter. Thecross-section of the catheter is shown in FIG. 21 b; the catheter couldbe manufactured by the cable extrusion technique that generally isapplied in fiber optics industry [Refer to the homepage of Optical CableCorporation.] Note that the central channel of the catheter is used tobe the conduit for the guidance of actuating liquid mentionedpreviously. There are also several conduits used to guide air flowing inand out the probing tip to balance the air pressure inside the OCTsystem (during operation, the free volume inside the probing tip changeswhile the twisted shaft 4 is moving). The diameter of the conduit isequal to that of the cylinder part 43 of the twisted shaft 4.

Part B in FIG. 21 a is simply a plate having fiber holding edges (405)and a rectangular central opening (401). This part could be made frommetal by using punching technology as is commonly applied in theindustry. In assembly, Part A and Part B are connected with glue such asepoxy. The lower stopper 34, which is required to constrain the twistedshaft 4 at its lower position, is formed together with the formation ofthe micro-balloon.

Micro-molding with polymeric material (such as SBS) could be used tofabricate the scanning head 1. The process of micro-molding requires aset of micro-molds. In this case, the fiber grooves 54 and thereflective surface 11 at the end of the fiber grooves 54 can be realizedby a set of micro-molds comprised of 18 edges (FIG. 22 a), each of whichhas the geometry shown in FIG. 22 b. As well, the central rectangularchannel could be molded by a rectangular shaft made by the equipment forthe fabrication of the twisted shaft 4. For the convenience of assembly,the scanning head 1 could be previously provided with the geometry shownin FIG. 22 c. The excess parts of the scanning head 1 would provideguidance and help with the alignment for the optical fibers 8. UV gluecould be used to fix the position of the optical fibers 8. The excessportion of the scanning head 1 could be cut off after the assembly ofthe optical fibers 8.

In another embodiment, laser beams heat at least three differentlocations on the surface of a micro-mirror 210, which is shown as a diskin FIGS. 23-25, successively. The micro-mirror 210 will provide awobbling corresponding to this kind of un-symmetric heating process, andan incident light (other than the heating laser) can be redirected in aswaying manner.

The heating process corresponds to the rotation period of themicro-minor 210 as required.

The micro-mirror 210 comprises two layers: a first layer 212 and asecond layer 214 (FIG. 23). At least one of the two layers can generatestructural deformation (contraction or expansion) by the application oflaser light. If the case is that both of the layers are deformable bylaser light, the sensitivities of the two layers to a same laser lightwould be set different to each others. FIG. 24 shows the perspectiveview of the micro-minor 210.

When the micro-minor 210 is irradiated with a laser beam, there will beexpansion or contraction in the layers. Because the expansion orcontraction within the layers is of different degrees (only one layer isdeformed or the two layers are deformed with different degrees), thestructure of the whole micro-mirror 210 will be twisted.

For example, in FIG. 25, when the section marked with the pie isirradiated with a laser beam, there is a deformation generated as shownin FIG. 26.

The material of the first and second layers 212, 214 could be metals orphotosensitive polymers.

In the case of metal layers, for example, the first layer 212 ispoly-silicon and the second layer 214 is gold. The mechanism of theexpansion or contraction within the layers is thermal expansion. Themetals will absorb the energy of a laser beam and be heated. Due todifferent thermal expansion coefficients of the two layers, thestructure will be twisted or bent. This will result in turning theminor, as shown in FIG. 26.

In the case of photosensitive polymers, for example, liquid crystalmaterials, the mechanism of the expansion or contraction inside thelayers is a phase change of the materials. Under the irradiation of alaser beam, the molecules of the polymeric materials will undergo phasechange, wherein the chemical structures of the materials are deformed,and a structural deformation occurs. Next, similar to the case of metallayers, the degrees of deformation of the two layers are different, andthere will be a twisting or bending effect in the structure of themicro-minor 210, and the effect in FIG. 26 is reached.

When the structure is twisted or bent by the application of laserenergy, the surface of the minor, shown in FIG. 24, can be tilted to aspecific direction. Therefore, one can control the direction of themicro-minor 210 by controlling the laser energy input.

The way to control the application of the laser light is to select thelocation on the micro-minor 210 to be irradiated by the laser beam, andcontrol the intensity of the laser. By controlling the location, one cancontrol the tilting direction of the mirror; and by controlling theintensity, one can control the tilting angle of the micro-minor 210.

Referring to FIG. 25 and FIG. 26, by continuously changing thelaser-shining location (FIG. 27), the tilting direction of themicro-mirror 210 can be continuously changed (FIG. 28). That is, themicro-mirror 210 could be rotated by changing the location of thelaser-shining.

This is the mechanism for the rotation of the laser-actuatedmicro-mirror 210.

As to the assembly of the whole OCT system (FIG. 29), the micro-minor210 is mounted on a base 216 connected to the tip end of the probe cover7. There is no object between the fibers and the mirror 210. Fiber 1,which is used to guide the detecting light, is the same fiber used inother embodiments of the OCT probe. The detecting light is redirected bythe tilting surface of the micro-mirror 210, such that it can scanaround by means of the tilting and rotating mirror 210. The fibers 2 areused to guide the actuating-laser light. As shown, at least three fibers2 are needed. The fibers 2 fire lasers in turns, such that they cangenerate continuous tilting effect as shown in FIG. 27 and FIG. 28.

The other features of the laser-actuating OCT probe are the same asthose described in other embodiments. For instance, the fiber 1 andfibers 2 are disposed in a fiber shaft holder 3.

After the fabrication by semiconductor technique, which is well known bythose skillful in the art, the minor is formed on a substrate (usuallysilicon substrate). The substrate material forms the base. Then a smallpiece is cut from the base that carries the minor from the substratewith a dicer. The small piece is mounted on to the tip's end by glue(EPDXY, for example).

Only one fiber 1 is enough to transmit the detecting light in thisembodiment. During operation, a circular scanning profile of thedetecting laser is realized. In this embodiment, illustrated in FIG. 30,the detecting laser is not centered to the mirror's center. Instead, thefollowing remain constant: (1) d, the distance between the mirror centerand the axis of the detecting light. (2) alfa, the angle between theminor surface and the axis of the detecting light. An open-loop systemis used for position feedback to properly arrange the periodical changeof the laser powers from the three fibers 2 to realize the constant alfaand d.

The position control is more complex than single-fiber 2 actuation.Particularly, the micro-mirror 210 needs a period of time to respondmechanically to the laser energy coming from the fiber 2. Even though itis known when and which of the fibers 2 are firing the laser power, theexact direction of the mirror surface information cannot be assured.

The absolute position of the minor is actually not necessary. Instead,speed-control is used to control the rotation of the scanning minor. Forexample, in the case of the minor driven by a transmission cable rotatedfrom outside, the exact position of the minor (which may be affected bya delay of cable transmission due to the cable's compliance) is not ofconcern; the rotation period of the mirror is controlled so that the“relative position” of the mirror is known. After receiving a continuousdata stream from the reflected detecting laser, the cross-section imageof the vessel is constructed by simply matching the data series to therotating period.

In this embodiment, the operation will be similar. What is different isthat the micro-mirror 210 is not actuated by a rotator but by threebimorph heat-deformable cantilever beams. This makes the control morecomplex. If only one of the fibers 2 fires at one time, it will be verydifficult if not impossible for the mirror to scan a circular profile asneeded. Instead, the three fibers 2 are needed to fire together, withdifferent powers, to bend the three cantilevers at different status atone time to match a circular scanning profile. The three cantilevers areactuated individually by the three fibers 2 such that they cooperatewith specific bending patterns that realize a circular scanning profileon the wall of the vessel.

In an alternative embodiment regarding the micro-mirror 210, the fibers1 and the fibers 2 are reversed so healing energy comes from a singlefiber 2 disposed preferably along the central axis of the tube. Theplurality of fibers 1 are disposed about the circumference of the tube.When the micro-minor 210 is irradiated by the laser beam from the fiber2, the laser energy causes the mirror to bend. By changing the intensityof the laser or pulsing the laser, motion can be imported to themicro-minor 210 which wires the probe tip to which it is attached, tomove back and forth, and thus the plurality of fibers 1 for scanning theinterior of the area of the patient in question.

Thermal expansion material normally can generate ˜5% of elongation for atemperature rise of 100° C. The length of the material inside the OCTprobe is originally 20 mm, which can therefore generate a thermalelongation of 1 mm. Polymers, including photosensitive polymers andshape memory polymers are able to generate >100% of photo-inducedelongations or shrinkages. The material inside the OCT probe isoriginally 1 mm, which can therefore generate a thermal elongation ofanother 1 mm.

Generally:

Optical tomographic instrumentation may be specified by spectrallyresolved bandwidth, which is equivalent to number of spectrallyresolvable cells. Each spectrally resolvable cell has a width δν, suchthat number of cells resolvable by the instrument isN_(instrument)=Δν/δν, where Δν is the available optical bandwidth ofsource light. The range of group-time delays the optical tomographicinstrument can resolve is given by: Δτ_(instrument)=1/δν. The smallestresolvable group-time delay the optical tomographic instrument canresolve is Δτ_(coherence)=1/Δν. Number of spectrally resolvable cellsthe optical tomographic instrument may resolve is given by:N_(instrument)=Δτ_(instrument)/Δτ_(coherence).

For one OCT A-scan into the object being imaged, the requirement fornumber of spectrally resolvable cells is −N_(A-scan)=Δz/L_(c),L_(c)˜c_(g)/Δν, Δz=imaging depth, L_(c) (coherence length), and c_(g) isthe group velocity of light in the object. N_(A-scan)=Δτ_(A-scan)Δν.Where Δσ_(A-scan)=Δz/c_(g) is the round-trip propagation time for lightto propagate from the most superficial and deepest position (to beimaged) in the object.

For some optical tomographic imaging instruments (e.g., those thatemploy narrow linewidth tunable laser sources or high resolutionspectrometers),N_(instrument)/N_(A-scan)=Δτ_(instrument)/Δτ_(instrument).

The above condition can be stated in three manners: 1) the number ofspectrally resolvable cells for the instrument (N_(instrument)) is muchgreater than that required for one A-scan (N_(A-scan)); 2) the range ofgroup time delays the instrumentation is capable of resolving(Δτ_(instrument)) is much greater than the group-time delay for a singleA-scan (Δτ_(A-scan)); 3) available optical bandwidth of source light(Δτ) is much greater than spectral width of each resolvable cell of theinstrumentation (δτ).

Because the instrument can resolve many more cells than that requiredfor one A-scan, multiplexing techniques are presented here toefficiently utilize the information carrying capacity (bandwidth)afforded by optical tomographic imaging instruments.

Selection criteria of multiplexing techniques employed may be derived inpart by the ratioN_(instrument)/N_(A-scan)=Δτ_(instrument)/Δτ_(instrument). Larger ratiosprovide a wider selection of possible multiplexing techniques and morecandidate domains (polarization, space, angle, temporal) to multiplexinto. Moreover, multiplexing spectral information into just one domain(e.g. spatial) is not the only envisioned approach. Generally,additional spectral information may be resolved into multiple domains(e.g., polarization and spatial).

Specific Implementations:

A. Polarization: The additional spectral cells may be used to recordinformation in the polarization domain using a system indicated in FIG.31. At least two incident polarization states 90° apart on the Poincaresphere are input into the interferometer. The polarization signature ofthe light reflected from the sample, such as a vessel wall or nervefiber layer, is compared to known polarization signatures of materials,such as plaques or a diseased nerve fiber layer. The reflected light andthus the material from which it was reflected is then identified. Thefiber delivery system described in PCT patent application numberPCT/US2004/012773, incorporated by reference herein, can be used.

The theory of operation of this approach is described using Muellermatrices or the spectrally-resolved Jones calculus. By inserting a fiberoptic spectral polarimetry instrument (FOSPI) in the detection path ofthe spectral domain optical coherence tomography (SD-OCT)instrumentation, the full set of Stokes parameters of lightbackscattered at the specific depth in the specimen can be obtainedwithout any other polarization controlling components inreference/sample/detection path of the interferometer and the priorknowledge of the polarization state of the light incident on the sample.In this configuration, two factors determine the spectral modulation.One is optical path length difference between the reference and samplesurface, (Δν), introduced by the common-path SDOCT and the other isphase retardations, Φ1(ν) and Φ2(ν) generated by the retarder system inthe FOSPI. Therefore, output from the presented single channelpolarization sensitive (PS)SD-OCT in the time-delay domain is theconvolution of the output from FOSPI and that from SD-OCT.

The Stokes parameters of light at the output of the interferometer areS_(i)=S_(i,1)+S_(i,2)+S_(i,i), where the first two terms are the Stokesparameters of light from the reference and sample path, respectively,and the last term is the contribution of interference. Consider thebirefringent sample with phase retardation δ and fast-axis oriented atangle of α. Then, the Stokes parameters of the light from the sample(S_(i,2)) and interference (S_(i,i)) are calculated in terms of theStokes parameters of light from the reference, S_(0,1), S_(1,1),S_(2,1), S_(1,3).

$\begin{matrix}{{{S_{0,2} = {r_{S}^{2}S_{0,1}}},{S_{1,2} = {{{r_{S}^{2}\left( {{\cos^{2}2\alpha} + {\cos\;\delta\;\sin^{2}2\alpha}} \right)}S_{1,1}} + {{r_{S}^{2}\left( {1 - {\cos\;\delta}} \right)}\sin\; 2\;\alpha\;\cos\; 2\alpha\; S_{2,1}} - {r_{S}^{2}\sin\;\alpha\;\sin\; 2\alpha\; S_{3,1}}}}}{S_{2,2} = {{{r_{S}^{2}\left( {1 - {\cos\;\delta}} \right)}\sin\; 2\alpha\;\cos\; 2\alpha\; S_{1,1}} + {{r_{S}^{2}\left( {{\sin^{2}2\;\alpha} + {\cos\;\delta\;\cos^{2}2\alpha}} \right)}S_{2,1}} - {r_{S}^{2}\sin\;{\alpha sin2}\;\alpha\; S_{3,1}}}}{S_{3,2} = {{r_{S}^{2}\sin\;\delta\;\sin\; 2\;\alpha\mspace{11mu} S_{1,1}} - {r_{S}^{2}\sin\;\delta\;\cos\; 2\alpha\; S_{2,1}} + {r_{S}^{2}\cos\; S_{3,1}}}}} & (1) \\{{S_{0,i} = {{2r_{S}\cos\;\Delta\;\cos\;\frac{\delta}{2}S_{0,1}} + {2r_{S}\sin\;\Delta\;\sin\;\frac{\delta}{2}\left( {{\cos\; 2\alpha\; S_{1,1}} + {\sin\; 2\alpha\; S_{2,1}}} \right)}}}{S_{1,i} = {{2r_{S}\cos\;{\Delta\left( {{\cos\;\frac{\delta}{2}S_{1,1}} - {\sin\;\frac{\delta}{2}\sin\; 2\;\alpha\; S_{3,1}}} \right)}} + {2r_{s}\sin\;\Delta\;\sin\;\frac{\delta}{2}\cos\; 2\alpha\; S_{0,1}}}}{S_{2,i} = {{2r_{S}\cos\;{\Delta\left( {{\cos\;\frac{\delta}{2}S_{2,1}} + {\sin\;\frac{\delta}{2}\sin\; 2\alpha\; S_{3,1}}} \right)}} + {2r_{s}\sin\;\Delta\;\sin\;\frac{\delta}{2}\cos\; 2\alpha\; S_{0,1}}}}{S_{3,i} = {2r_{S}\cos\;{\Delta\left( {{\sin\;\frac{\delta}{2}\sin\; 2\;\alpha\; S_{1,1}} - {\sin\;\frac{\delta}{2}\cos\; 2\alpha\; S_{2,1}} + {\cos\;\frac{\delta}{2}S_{3,1}}} \right.}}}} & (2)\end{matrix}$with a reflection coefficient of the sample r_(s) and an optical pathlength difference between the sample and reference path Δ. Here, theterms including trigonometric functions of Δ represent the interferencebetween the light from reference and sample paths.

The measured intensity from SDOCT passing through the FOSPI for abirefringent sample, then, is

$\begin{matrix}{{\left. {{I_{out}^{(i)}(v)} = {{r_{s}\cos\;\Delta\;\cos\;\frac{\delta}{2}S_{0,1}} + {r_{s}\sin\;\Delta\;\sin\;\frac{\delta}{2}\left( {{\cos\; 2\alpha\; S_{1,1}} + {\sin\; 2\alpha\; S_{2,1}}} \right)} + {\frac{1}{2}{r_{s}\left\lbrack {{\left( {{\cos\;\frac{\delta}{2}S_{1,1}} - {\sin\;\frac{\delta}{2}\sin\; 2\alpha\; S_{3,1}}} \right){\cos\left( {\Delta - \phi_{2}} \right)}} + {\sin\;\frac{\delta}{2}\cos\; 2\;\alpha\; S_{0,1}{\sin\left( {\Delta - \phi_{2}} \right)}}} \right\rbrack}} + {\frac{1}{2}{r_{s}\left\lbrack {{\left( {{\cos\;\frac{\delta}{2}S_{2,1}} - {\sin\;\frac{\delta}{2}\sin\; 2\alpha\; S_{3,1}}} \right){\cos\left( {\Delta - \phi_{2}} \right)}} + {\sin\;\frac{\delta}{2}\cos\; 2\alpha\; S_{0,1}{\sin\left( {\Delta\; - \phi_{2}} \right)}}} \right\rbrack}} + {\frac{1}{4}{r_{s}\left\lbrack {{\left( {{\cos\;\frac{\delta}{2}S_{2,1}} + {\sin\;\frac{\delta}{2}\cos\; 2\;\alpha\; S_{3,1}}} \right){\cos\left( {\Delta - \phi_{2} + \phi_{1}} \right)}} + {\left\{ {{\sin\;\frac{\delta}{2}\sin\; 2{\alpha\left( {S_{0,1} + S_{1,1}} \right)}} - {\sin\;\frac{\delta}{2}\cos\; 2\alpha\; S_{2,1}} +}\quad \right.{\quad\quad}\cos\;\left. \quad{\frac{\delta(v)}{2}S_{3}^{(1)}} \right\}}}\quad \right.}\left. \quad{\sin\left( {\Delta - \phi_{2} + \phi_{1}} \right)} \right\rbrack} + {\frac{1}{4}{r_{s}\left\lbrack {{\left( {{\cos\;\frac{\delta}{2}S_{2,1}} + {\sin\;\frac{\delta}{2}\cos\; 2\alpha\; S_{3,1}}} \right){\cos\left( {\Delta + \phi_{2} - \phi_{1}} \right)}} + \left\{ {{\sin\;\frac{\delta}{2}\sin\; 2{\alpha\left( {S_{0,1} + S_{0,1}} \right)}} + {\sin\;\frac{\delta}{2}\cos\; 2\alpha\; S_{2,1}} -}\quad \right.}\quad \right.}\cos\;\frac{\delta}{2}S_{3,1}}}} \right\}\left\lbrack {\sin\left( {\Delta + \phi_{2} - \phi_{1}} \right)} \right\rbrack} - {\frac{1}{4}{r_{s}\left\lbrack {{\left( {{\cos\;\frac{\delta}{2}S_{2,1}} + {\sin\;\frac{\delta(v)}{2}\cos\; 2\alpha\; S_{3,1}}} \right){\cos\left( {\Delta - \phi_{2} - \phi_{1}} \right)}} + \left\{ {{\sin\;\frac{\delta}{2}\sin\; 2{\alpha\left( {S_{0,1} + S_{1,1}} \right)}} + {\sin\;\frac{\delta}{2}\cos\; 2\alpha\; S_{2,1}} -}\quad \right.}\quad \right.}{\quad{\left. \quad{\cos\;\left. \quad{\frac{\delta}{2}S_{3,1}} \right\}{\sin\left( {\Delta - \phi_{2} - \phi_{1}} \right)}} \right\rbrack - {\left\lbrack {\left( {{\cos\;\frac{\delta}{2}S_{2,1}} +}\quad \right.{\quad\quad}}\quad \right.\sin}}\;\quad}{\quad{\frac{\delta(v)}{2}\cos{\left. \quad\;{{{\quad{2\alpha}\quad}\left. \quad\;{\left. \quad S_{3,1} \right){\cos\left( {\quad{\left. \quad{\Delta - \phi_{2} - \phi_{1}} \right) +}\quad}\quad \right.}\left\{ \sin\;\quad \right.{\quad{\frac{\delta}{2}\sin}\;\quad}\left. \quad{2{\alpha\left( {\left. \quad{S_{0,1} + S_{1,1}} \right) + {\sin\;\frac{\delta}{2}\cos\; 2\alpha\; S_{2,1}} -}\quad \right.}\cos\;\frac{\delta}{2}S_{3,1}} \right\}{\sin\left( {\Delta - \phi_{2} - \phi_{1}} \right)}} \right\rbrack} - {\frac{1}{4}{r_{s}\left\lbrack {{\left( {{\cos\;\frac{\delta}{2}S_{2,1}} + {\sin\;\frac{\delta}{2}\cos\; 2\;\alpha\; S_{3,1}}} \right){\cos\left( {\Delta + \phi_{2} + \phi_{1}} \right)}} + {\left\{ {{\sin\;\frac{\delta}{2}\sin\; 2\;{\alpha\left( {S_{0,1} + S_{1,1}} \right)}} - {\sin\;\frac{\delta}{2}\cos\; 2\alpha\; S_{2,1}} +}\quad \right.\cos\;\frac{\delta}{2} S_{3,1}}} \right\}}{\sin\left( {\Delta - \phi_{2} - \phi_{1}} \right)}}} \right\rbrack.}}}}} & (3)\end{matrix}$for the interference signal. Fourier transform of equation (3) givesseven components in the positive optical path length difference domainwhich are centered at Δ, Δ±φ2, Δ±(φ2−φ1), Δ±(φ2+φ1), respectively.Inverse Fourier transforms of each component are as follows:

$\begin{matrix}{{\Delta\text{:}\frac{1}{2}r_{s}{\mathbb{e}}^{{\mathbb{i}}\;\Delta}\left\{ {{\cos\;\frac{\delta}{2}S_{0,1}} - {{\mathbb{i}}\;\sin\frac{\delta}{2}\left( {{\cos\; 2\alpha\; S_{1,1}} + {\sin\; 2\alpha\; S_{2,1}}} \right)}} \right\}},} & (4) \\{{\Delta + {\varphi_{2}\text{:}\frac{1}{4}r_{s}{\mathbb{e}}^{{\mathbb{i}}\;\phi_{2}}{\mathbb{e}}^{{\mathbb{i}}\;\Delta}\left\{ {\left( {{\cos\;\frac{\delta}{2}S_{1,1}} - {\sin\;\frac{\delta}{2}\sin\; 2\;\alpha\; S_{3,1}}} \right) - {{\mathbb{i}}\;\sin\;\frac{\delta}{2}\cos\; 2\alpha\; S_{0,1}}} \right\}}},} & (5) \\{\Delta + \varphi_{2} - {\varphi_{1,0}\text{:}\frac{1}{8}r_{s}{\mathbb{e}}^{{\mathbb{i}}{({\phi_{2} - \phi_{1}})}}{{\mathbb{e}}^{{\mathbb{i}}\;\Delta}\left\lbrack {\left( {{\cos\;\frac{\delta}{2}S_{1,1}} + {\sin\;\frac{\delta}{2}\cos\; 2\alpha\; S_{3,1}}} \right) - {{\mathbb{i}}\left\{ {{\sin\;\frac{\delta}{2}\sin\; 2{\alpha\left( {S_{0,1} - S_{1,1}} \right)}} + {\sin\;\frac{\delta}{2}\cos\; 2\;\alpha\; S_{2,1}} - {\cos\;\frac{\delta}{2}S_{3,1}}} \right\}}} \right\rbrack}}} & (6) \\{\Delta + \varphi_{2} - {\varphi_{1}\text{:}} - {\frac{1}{8}r_{s}{\mathbb{e}}^{{\mathbb{i}}{({\phi_{2} + \phi_{1}})}}{{\mathbb{e}}^{\mathbb{i}\Delta}\left\lbrack {\left( {{\cos\;\frac{\delta}{2}S_{2,1}} + {\sin\;\frac{\delta}{2}\cos\; 2\;\alpha\; S_{3,1}}} \right) - {{\mathbb{i}}\left\{ {{\sin\;\frac{\delta}{2}\sin\; 2{\alpha\left( {S_{0,1} + S_{1,1}} \right)}} - {\sin\frac{\delta}{2}\cos\; 2\;\alpha\; S_{2,1}} + {\cos\;\frac{\delta}{2}S_{3,1}}} \right\rbrack}} \right.}}} & (7)\end{matrix}$

Comparing with equation (2), real part of equation (4) gives S_(0,i)/4and real part of equation of (5) after shifting the phase by −Φ₂ givesS_(1,i)/8. Likewise, S_(2,i)/8 and S_(3,i)/8 can be obtained by takingthe real part of subtraction of (7) from (6) and the imaginary part ofaddition of (6) and (7) after the appropriate phase shift, −(Φ₂−Φ₁) and−(Φ₂+Φ₁) for (6) and (7), respectively. Moreover, simple arithmeticgives phase retardation due to the birefringence of the sample, δ,without knowledge of incident polarization state. The real part of (4),imaginary part of (5), the imaginary part of subtraction of (7) from (6)are

$\begin{matrix}{{\frac{1}{2}r_{s}\cos\;\frac{\delta}{2}S_{0,1}},} & (8) \\{{\frac{1}{4}r_{s}\sin\;\frac{\delta}{2}\cos\; 2\alpha\; S_{0,1}},} & (9) \\{{\frac{1}{4}r_{s}\sin\;\frac{\delta}{2}\sin\; 2\;\alpha\; S_{0,1}},} & (10)\end{matrix}$after the phase shift by −Δ, −(Δ+Φ₂), −(Δ+Φ₂−Φ₁) and −(ΔΦ₂+Φ₁),respectively. With a trigonometric identity, the following can beobtained

$\begin{matrix}{{{\tan\;\frac{\delta}{2}} = \frac{2\sqrt{(9)^{2} + (10)^{2}}}{(8)}},} & (11)\end{matrix}$

Phase retardation due to birefringence [FIG. 36] and fast-axis angle[FIG. 37] of the birefringent sample were estimated from interferencebetween the back surface of the glass window and the back surface of thebirefringent sample by using the equations above. For this measurement,the birefringent sample was rotated in 5° increments from 0° to 90°. Anestimated single-pass phase retardation of 34.06°+/−2.68° is consistentwith a value deduced from the manufacturer's specification (31.4°). Theestimated fast-axis angle is shown in FIG. 37 and is plotted withrespect to orientation of the birefringent sample.

The results show practical demonstration of polarization multiplexing.

B. Space or Lateral Position: The additional spectral cells may be usedto record information in the space or lateral position domain using asystem indicated below.

1. Existing Multifiber Approach: (described above)

2. Spatially Scanned Light:

The schematic of the experimental setup of a fiber-based spatiallymultiplexed swept source OCT (SM-SS-OCT) system is depicted in FIG. 32using the system described in PCT patent application numberPCT/US2004/012773, incorporated by reference herein, where the top ispreferably rotated at least 100 times for each position.

A tunable laser and spectrum analyzer (TLSA 1000, Precision Photonics,Inc.) that operates in the 1520-1620 nm wavelength range (λ₀=1570 nm)with FWHM spectral line width specified at 150 KHz is used as theilluminating source and is equipped with an optical isolator to protectthe laser from spurious reflections. The laser output is coupled intoone arm of a 2×2 fiber-based coupler (interferometer). The 50%-50%coupler splits this beam into two nearly equal parts, used in thereference and sample arms, respectively. The reference arm has a fixedpath length, and simply consists of a fixed minor that reflects theentire light incident upon it back into the fiber-based coupler. Thelight exiting the sample arm of the interferometer is collimated, andscanned across the sample by a scanning galvanometer and a focusinglens. The scanning galvanometer and focusing lens is used to rapidlyscan the lateral positions of the tissue. The TLSA 1000 completes onecomplete wavelength sweep in approximately one second. Within this time,the galvanometer is programmed to sweep all lateral positions of thetissue several hundred times. Light returning from the sample interfereswith the light from the fixed reference in the fiber-basedinterferometer, and the resultant spectral interference signal (due topath length variations between sample and reference reflections) isdetected by a photodetector placed in the detection arm of the system.The electrical output is digitized, and a non-uniform Fourier Transform(NUFT) of each A-line spectral data gives the depth profile of thesample reflectance. FIGS. 34 and 35 are images of a 100 micron thickslide recorded with the spatially multiplexed OCT system. The images areof the same object (microscope cover glass) only for one image (FIG. 34)the intensity of the light returning from the sample is displayed on alinear greyscale, while in the other image (FIG. 35) the intensity ofthe light returning from the sample is displayed according to logarithmof the intensity.

C. Angle: The additional spectral cells may be used to recordinformation in the angle domain using a system indicated in FIG. 33.

FIG. 33 depicts a Multi Fiber Angle-domain OCT system. The output of thefrequency-swept source A is split into n fibers through the splitter B.The light passes through the circulators C, is collimated, focusedthrough a lens, contacts the tissue, and then is reflected into any ofthe multiplicity of fibers. A reference reflector for each path isintroduced into each fiber segment. For example, the reference reflectorcan be positioned at the terminal end of each fiber segment. For eachi'th input fiber segment, interference is formed between lightbackscattered from the tissue and into the j'th fiber and the referencereflection from the j'th fiber. For N fibers, N² interference fringesare formed each corresponding to an incident (α_(i)) and backscatteredangle (β_(j)). Light intensity in the spectral domain is then convertedto a voltage through a photoreceiver, which outputs to an ADC board,which is read into a computer. This system allows phase-sensitive angleresolved imaging of discrete light paths in and out-of the specimen.Using space-spatial frequency transformation (e.g., two-dimensionalFourier transformation) lateral structures can be imaged withsub-wavelength resolution.

D. Space-Angle combinations (e.g. x dimension-space, y dimension-angle):The space and angle dimensions may be combined to form systems that usethe additional spectral cells image both space and angles. For example,additional spectral cells may be used to record position information inone dimension (e.g. x) and angle information in the orthogonal dimension(y).

Although the embodiments disclosed herein have been described in detailin the foregoing embodiments for the purpose of illustration, it is tobe understood that such detail is solely for that purpose and thatvariations can be made therein by those skilled in the art withoutdeparting from the spirit and scope of the embodiments disclosed hereinexcept as it may be described by the following claims.

What is claimed is:
 1. An endoscope for a patient comprising: a lightsource operably coupled to an optical fiber array comprising a pluralityof optical fibers adapted to be disposed in the patient, the opticalfiber array including a tube about which the plurality of optical fibersare disposed, wherein the tube has grooves that extend longitudinallyalong the tube, one of the plurality of optical fibers disposed in eachof the grooves, the optical fiber array including a probe tip having areflector disposed in each groove which reflects the light from theoptical fiber in the groove when the reflector is in the patent andreflects light from the patient to the optical fiber when the array isin the patient, the optical fiber array transmitting the light from thelight source into the patient, and transmitting the light reflected bythe patient out of the patient, the plurality of the optical fibers ofthe array in optical communication with the light source; and a detectorfor receiving the light from the array and analyzing the light, theplurality of the optical fibers of the array in optical communicationwith the detector.
 2. An endoscope as described in claim 1, wherein thelight source includes a tunable laser source and an optical fiber forguiding the light from the light source to the plurality of opticalfibers of the array.
 3. An endoscope as described in claim 2, whereinthe optical fiber is single mode, has a core with cladding disposedabout the core, and has a lens at its tip which focuses the light fromthe core to the reflector and light from the reflector to the core. 4.An endoscope as described in claim 3, wherein the array furthercomprises a transparent cover.
 5. An endoscope as described in claim 4,further comprising an input arm operably coupled to the light source,the array comprises a sample arm, the detector comprises a reference armand a detector arm; wherein the input arm, the detector arm, the samplearm and the reference arm together form an interferometer.
 6. Anendoscope as described in claim 5, wherein the reference arm uses RSODto introduce depth scanning and dispersion compensation to theinterferometer.
 7. An endoscope as described in claim 6, furthercomprising an opto-coupler which optically couples light from the inputarm into corresponding optical fibers of the sample arm.
 8. An endoscopeas described in claim 1, wherein the probe tip further comprises ascanning head which holds N optical fibers, where N is greater than orequal to 2 and is an integer.
 9. An endoscope as described in claim 8,wherein the N optical fibers are arranged around the scanning head inparallel and equal spacing.
 10. An endoscope as described in claim 9,wherein the probe tip includes a mechanism for moving the scanning headso each of the optical fibers scan an angular range of 360/N degrees.11. An endoscope as described in claim 10, wherein the moving mechanismincludes a mechanism for linear motion which causes the scanning head torotate.
 12. An endoscope as described in claim 11, wherein the linearmotion mechanism includes a fiber shaft holder having a shaft channelextending axially along the holder, and N fiber channels are arrangedaround the holder in parallel with the shaft channels, and a twistingshaft that fits in and conforms with the shaft channel, wherein as thetwisting shaft moves in the shaft channel, the holder rotates.
 13. Anendoscope as described in claim 12, wherein the scanning head has asocket head that conforms with the shaft and causes the scanning head torotate.
 14. An endoscope as described in claim 1, further comprising alight activated material that turns at least a portion of the tube whenlight is received by the light activated material.
 15. An endoscope asdescribed in claim 1, wherein the light source comprises a spectrallyresolved bandwidth and the spectrally resolved bandwidth includes aplurality of spectrally resolved cells.
 16. An endoscope for a patientcomprising: a light source; an optical fiber array comprising aplurality of optical fibers adapted to be disposed in the patient, theoptical fiber array including a tube about which the plurality ofoptical fibers are disposed, wherein the tube has grooves that extendlongitudinally along the tube, one of the plurality of optical fibersdisposed in each of the grooves, the optical fiber array operablycoupled to a twisted shaft to impart rotational motion to the opticalfiber array, the optical fiber array transmitting the light from thelight source into the patient, and transmitting the light reflected bythe patient out of the patient, the plurality of optical fibers of thearray in optical communication with the light source; and a detector forreceiving the light from the array and analyzing the light, theplurality of optical fibers of the array in optical communication withthe detector.
 17. An endoscope as described in claim 16, furthercomprising a fiber-shaft holder including a tubular structure and ashaft channel through which the twisted shaft is coaxially disposed;wherein the shaft channel includes a geometry that is reduced from around cross-sectional area to a rectangular cross-sectional area.
 18. Anendoscope as described in claim 17, wherein the twisted shaft includes arectangular cross-section identical to the geometry of the rectangularcross-sectional area of the shaft channel.
 19. An endoscope as describedin claim 18, wherein the twisted shaft includes a non-twisted portionand a twisted portion, and the twisted shaft slides back and forth viathe rectangular cross-sectional area of the shaft channel.
 20. Anendoscope as described in claim 19, further comprising a linear motionmechanism operably coupled to the twisted shaft.